Patents have named inventors, which can not be companies: they have to be people.
When someone works for a company (actually because of this rule that patents are assigned to individual inventors) they agree as a condition of employment to "assign" the rights to any patents awarded to them in conjunction with performing work for the company (and sometimes not when doing so also) to said company.
So, did they company pay for filing of a patent with you as a named inventor? If so then you signed away the rights to this patent (or you did if they have their legal paperwork straight). You own it as much as I do. You might try asking them nicely for a license to use it -- they might be inclined to help you since to some extent they also need your good will for any future litigation over said patent.
Or, did someone else at the company file a patent covering something that you believe you (not them) invented? If so then prepare to open a legal can of worms.
I guess you might also be saying that the company filed a patent with or without you as a named inventor that you believe is weak (not really a patentable invention) and you're wondering if this is any different than the likely 1000 other weak patents out there covering the same "invention"?
Perhaps if you post more details on the specifics of the situation folks here can help with more accurate advice.